Separating 1-chloro-2,2,2-trifluoro-ethyl difluoromethyl ether from 1-chloro-2,2,2-trifluoroethyl difluorochloro-methyl ether by azeotropic distillation

ABSTRACT

Azeotropes of 1-chloro-2,2,2-trifluoroethyl difluoromethyl ether and acetone, methyl ethyl ketone or tetrahydrofuroan are formed and used to separate this ether from 1-chloro-2,2,2trifluoroethyl difluorochloromethyl ether.

United States Patent Croix 1March 13, 1973 SEPARATING l-CHLORO-2,2,2-[56] References Cited TRIFLUORO-ETHYL DIFLUOROMETHYL ETHER FROM 1-UNITED STATES PATENTS CHLOR0-2,2,Z-TRIFLUOROETHYL 3,535,388 10 1970T611611 ..260/614 F DIFLUOROCHLORO-METHYL ETH R 3,501,533 3 1970 Anelloet al. ..260/616 x BY AZEOTROPIC DISTILLATION 3,406,099 10/1968 Buckmanet a] "203162 X 3,282,801 11/1966 Wiist ..203 62 x [75] Invent Lou'seSummlt, 2,442,589 6/1948 Evans et al. ..203 62 [73] Assignee: Airco,Inc., New York, NY.

' Primary Examiner-Norman Yudkoff 2 l d: 1971, 2] Fle Aug 2 AssistantExaminerDavid Edwards p 0: 168,399 Attorney-Roger M. Rathbun et al.

[52] US. Cl. ..203/58, 203/62, 260/614 F, [57] ABSTRACT 260/616Azeotropes of l-chloro-2,2,2-trifluoroethyl [51] lnt.Cl. ..B0ld 3/36 h lh d h l h 1k [58] Field of Search ..203/62,58,57;260/6l4 F, Y acetmemetY Y or tetrahydrofuroan are formed and used to separate this ether froml-chloro-Z ,2,2-trifluoroethyl difluorochloromethy] ether.

' 8 Claims, No Drawings SEPARATING l-CHLOR-2,2,2-TRIFLUORO- ETHYLDIFLUOROMETHYL ETHER FROM 1- CHLORO-2,2,Z-TRIFLUOROETHYLDIFLUOROCHLORO-METHYL ETHER BY AZEOTROPIC DISTILLATION This inventionrelates to the purification of l-chloro- 2,2,2trifluoroethyldifluoromethyl ether having the formula CF CHClO-CHF,. Moreparticularly, the invention concerns the purification of 1-chloro-2,2,2-trifluoroethyl difluoromethyl ether by separation from l-chloro-2 ,2,2-trifluoroethyl difluorochloromethyl ether through the formation of anazeotrope of 1- chl0ro-2,2,2-trifluoroethyl difluoromethyl ether andacetone, methyl ethyl ketone or tetrahydrofuran. The invention is alsodirected to these azeotropes as new compositions of matter.

U. S. Pat. Nos. 3,535,388 and 3,535,425 describe the preparation of1-chloro-2,2,Z-trifluoroethyl difluoromethyl ether and methods formaking this material which is useful, for instance, as an anesthetic. Inone method of the manufacture of l-chloro-2,2,2- trifluoroethyldifluoromethyl ether according to these patents, 2,2,2-trifluoroethyldifluoromethyl ether is chlorinated to obtainl-chloro-2,2,2-trifluoroethyl difluoromethyl ether in admixture withother halogenated ethyl methyl ethers. Some of the halogenated etherby-products have boiling points sufficiently far from that ofl-chloro-2,2,Z-trifluoroethyl difluoromethyl ether so that the lattercan be separated by very careful fractional distillation. Theby-products, l-chloro-2 ,2 ,2-trifluoroethyl difluorochloromethyl ether(CF CHClO-CF Cl), however, co-distills withl-chloro-2,2,2-trifluoroethyl difluoromethyl ether at about 2 percentconcentration so the separation of the latter in high purity bydistillation cannot be accomplished. Another means for separatingl-chloro-2,2,2- trifluoroethyl difluoromethyl ether from the otherethers is by vapor/liquid chromatography, but this type of operation isslow, expensive and not readily adaptable to preparingl-chloro-2,2,Z-trifluoroethyl difluoromethyl ether in commerciallydesirable quantities. Especially when l-chloro-2,2,2-trifluoroethyldifluoromethyl ether is intended for use as an anesthetic, a puritygreater than 99.95 percent is needed, and it is thus apparent that moredesirable ways of purifying l-chloro-2,2,Z-trifluoroethyl difluoromethylether are needed.

In the method of the present invention, l-chloro- 2,2,2-trifluoroethyldifluoromethyl ether is separated from its mixture withl-chloro-2,2,2-trifluoroethyl difluorochloromethylether by forming anazeotrope of l-chloro-2,2,Z-trifluoroethyl difluoromethyl ether withacetone, methyl ethyl ketone or tetrahydrofuran. The resulting maximumboiling point azeotropes boil sufficiently above the boiling point ofl-chloro-2,2,2- trifluoroethyl difluoromethyl ether, to enable the readydistillation from the azeotropes of the materials in the mixture whichboil close to l-chloro-2,2,2- trifluoroethyl difluoromethyl ether,especially 1- chloro-2,2,2-trifluoroethyl difluorochloromethyl ether.Often the by-product ethers are a minor part by weight of their mixturewith l-chloro-2,2,2-trifluoroethyl difluoromethyl ether.

The azeotrope of acetone and l-chloro-2,2,2- trifluoroethyldifluoromethyl ether contains a molar ratio of acetone tol-ch1oro-2,2,2-trifluoroethyl difluoromethyl ether of about 1.2:1 asdetermined by gas chromatography, and the azeotrope boils at atemperature of about 66C. The azeotropes of l-chloro-2,2,2-trifluoroethyl difluoromethyl ether and tetrahydrofuran and methylethyl ketone boil at about 68C. and 81C., respectively. Thetetrahydrofuran azeotrope has a molar ratio of tetrahydro-furan to 1-chloro2,2,2-trifluoroethyl difluoromethyl ether of about 3:1, whileazeotrope of methyl ethyl ketone and l-chloro-2,2,2-trifluoroethyldifluoromethyl ether contains the components in a molar ratio of about5.5:1. These molar ratios are as determined by gas chromatography andthe boiling points reported are at atmospheric pressure.

The fact that l-chloro-2 ,2 ,2-trifluoroethyl difluoromethyl ether hasbeen found to form these azeotropes offers a convenient way ofseparating the ether from close boiling materials which do not formsimilar boiling azeotropes with acetone, methyl ethyl ketone ortetrahydrofuran. The l-chloro-2,2,2- trifluoroethyl difluoromethyl etherazeotropes are par ticularly useful in separating the ether from '1-chloro- 2,2,2-trifluoroethyl difluorochloromethyl ether which appearsas a minor byproduct, for instance, less than about Spercent and oftenat least about 1 percent by weight, in the product from synthesis ofl-chloro-2,2,2- trifluoroethyl defluoromethyl ether by the procedurenoted'above. These reaction products frequently contain about 85 to 98percent of l-chloro-2,2,2- trifluoroethyl difluoromethyl ether and mayalso include other by-product ethers which boil considerably belowl-chloro-2,2,2-trifluoroethyl difluoromethyl ether, and thus if desiredthese lower boiling ethers can be readily separated by distillation fromthe reaction mixture before formation of the azeotrope of thisinvention. Alternatively, these lower boiling products which are alsousually present in minor amounts by weight can be removed from thel-chloro- 2,2,2- trifluoroethyl difluoromethyl ether-containing reactionmixture after the formation of the azeotrope, unless the lower boilingmaterials form azeotropes with acetone,

methyl ethyl ketone or tetrahydrofuran having boiling points close tothe given azeotrope of l-chloro-2,2,2- trifluoroethyl difluoromethylether.

In performing the separation of l-chloro-2,2,2- trifluoroethyldifluoromethyl ether according to this invention, acetone, methyl ethylketone or tetrahydrofuran is used in an amount sufficient to form anazeotrope with a substantial portion of the l-chloro-2,2,2-trifluoroethyl difluoromethyl ether present in its admixture withl-chloro-2 ,2 ,2 -trifluoroethyl difluorochloromethyl ether. In order torecover maximum amounts of l -chloro-2,2,2-trifluoroethyl difluoromethylether it is normally desirable to combine at least sufficient of theacetone, methyl ethyl ketone or tetrahydrofuran to azeotropesubstantially all of the l-chloro-2,2,2-trifluoroethyl difluoromethylether present in the mixture to be treated. Large excesses of acetone,methyl ethyl ketone or tetrahydrofuran are not necessary and may serveto increase the cost of the operation. Generally, the amount of acetone,methyl ethyl ketone or tetrahydrofuran combined with the l-chloro-2,2 ,2-trifluoroethyl difluoromethyl ether containing close boiling materials,

is conveniently about 0.1 to or more, preferably about 1 to 7, moles permole of l-chloro-2,2,2- trifluoroethyl difluoromethyl ether in themixture to be separated, although as indicated above at least enough ofthe acetone, methyl ethyl ketone or tetrahydrofuran is preferablycombined to azeotrope substantially all of thel-chloro-2,2,2-trifluoroethyl difluoromethyl ether present. Thepreferred amount of acetone combined with thel-chloro-2,2,2-trifluoroethyl difluoromethyl ether-containing mixture isabout 0.3 to 3 moles of acetone per mole of this ether in the mixturetreated, while similar preferred amounts in the case of tetrahydrofuranand methyl ethyl ketone are, respectively, about 2 to 5 and about 4 to 7moles per mole of this desired ether in the mixture.

After combination of the acetone, methyl ethyl ketone or tetrahydrofuranwith the l-chloro-2,2,2- trifluoroethyl difluoromethyl ether mixture tobe separated in accordance with this invention, thelchloro-2,2,2-trifluoroethyl difluorochloromethyl ether can be easilyfractionally distilled from the mixture. The resultingl-chloro-2,2,2-trifluoroethyl difluoromethyl ether azeotrope can then betreated to yield a highly pure, e.g. greater than 99.95% pure, l-chloro-2,2,2-trifluoroethyl difluoromethyl ether product by separation fromacetone, methyl ethyl ketone or tetrahydrofuran according to which ofthese latter materials has been employed to form the azeotrope. Theazeotrope can be treated by water extracting the acetone, methyl ethylketone or tetrahydrofuran from the l-chloro-2,2,2-trifluoroethyldifluoromethyl ether, but a more preferred procedure is to add water tothe azeotrope, for instance, in an amount of about 0.5 to 5, preferablyabout 1 to 3, parts by weight of water per part ofl-chloro-2,2,2-trifluoroethyl difluoromethyl ether in the azeotrope. Bysubsequent fractional distillation relatively purel-chloro-2,2,Z-trifluoroethyl difluoromethyl ether can be readilyseparated as an overhead vapor in high yields.

The present invention is further illustrated by the following examples:

EXAMPLES [-1]! A crude mixture (2000 g.) of l-chloro-2,2,2-trifluoroethyl difluoromethyl ether of the following composition asdetermined by vapor phase chromatography:

was mixed with 864 g. acetone with noticeable evolution of heat whenstirred. This mixture was distilled through a 50 plate fractionatingcolumn of protruded packing to separate a first cut (154 g.) (bp.30-59C.) of acetone and all of the two impurities, CF,CH,-O- CFCI and CFCH,O-CF,H. A second cut (bp. 6067C.) (449 g.) was collected, containingmost of the CF,CHCIOCF,CI, 60-70 percent acetone and a small quantity ofCF,CHClO-CF,H. At the point where the concentration of CF CHClO--CF,Clwas less than 0.01 percent in both the pot and the distillate,

the distillation was stopped, and 3000-4000 g. of water was added to thepot and the distillation resumed. There was then distilled overhead at4849C., 1299 g. of CF CHClOCF, of greater than 99.95 percent purity.Similar separations can be made by substituting for the acetone, 4500 g.methyl ethyl ketone or 2500 g. tetrahydrofuran.

EXAMPLE lV Composition of Acetone-CF,CHCIOCHF Azeotrope When equalweight quantities of CF,-,CHCl-O CHF, and acetone were distilled on asmall fractionating column, the boiling point passed that of CF;,CHCl--O--CHF, (48.5C.) and some free acetone (56.5C.) was the first cut. Theboiling point then stabilized at 66, u 1.3269, with a composition of46.8 percent acetone and 53.2 percent CF CHClO-CHF (area percent by gaschromatography), 27.5 percent by weight acetone, 72.5 percent by weightCF CHCl O-CHF 1.2 to 1.0 molar ratio.

EXAMPLE V Tetrahydrofuran CRCHCl-O-CHF, Azeotrope When a mixture of 2parts by weight of tetrahydrofuran and 1 part by weight of CF-,CHCl-OCHF was distilled on a small fractionating column, a constantboiling fraction was obtained at 68C., n 1.3660. The composition by gaschromatography analysis was 65.7 percent tetrahydrofuran and 33.6percent CF CHCl-OCHF (53.6 percent by weight tetrahydrofuran and 46.4percent byweight CF CHCl-OCHF,, 3:1 molar ratio).

EXAMPLE VI Methyl Ketone CF CHCl-OCHF Azeotrope When equal parts byweight of methyl ethyl ketone and CF CHClOCHF were distilled on a smallfractionating column, a constant boiling fraction was obtained at 81C.The composition by gas chromatography analysis was 80.2 percent methylethyl ketone and 19.8 percent CF CHCL0-CHF, (68.5 percent by weightmethyl ethyl ketone and 31.5 percent by weight CF;,CHCl-OCHF,, 5.5:lmolar ratio).

It is claimed:

1. A method of separating l-chloro-2,2,2- trifluoroethyl difluoromethylether from its mixture with l-chloro-2,2,Z-trifluoroethyldifluorochloromethyl ether which comprises combining said mixture with amember selected from the group consisting of acetone, methyl ethylketone and tetrahydrofuran to form a higher boiling azeotrope withl-chloro-2,2,2-trifluoroethyl difluoromethyl ether, and distillingl-chloro-2,2,2-trifluoroethyl difluorochloromethyl ether from saidazeotrope.

2. The method of claim 1 in which the selected member is acetone.

3. The method of claim 1 in which the selected member is methyl ethylketone.

4. The method of claim 1 in which the selected member istetrahydrofuran.

Ethyl 6 5.The method ofclaim l in which water is combined 7. The methodof claim 5 in which the selected with said azeotrope after saiddistilling and l-chlorob i methyl ethy1kemne 2,2,2-trifluoroethyldifluoromethyl ether is distilled from the mixture.

6. The method of claim 5 in which the selected member is acetone. 1"

8. The method of claim 5 in which the selected 5 member istetrahydrofuran.

1. A method of separating 1-chloro-2,2,2-trifluoroethyl difluoromethylether from its mixture with 1-chloro-2,2,2-trifluoroethyldifluorochloromethyl ether which comprises combining said mixture with amember selected from the group consisting of acetone, methyl ethylketone and tetrahydrofuran to form a higher boiling azeotrope with1-chloro-2,2,2-trifluoroethyl difluoromethyl ether, and distilling1-chloro-2,2, 2-trifluoroethyl difluorochloromethyl ether from saidazeotrope.
 2. The method of claim 1 in which the selected member isacetone.
 3. The method of claim 1 in which the selected member is methylethyl ketone.
 4. The method of claim 1 in which the selected member istetrahydrofuran.
 5. The method of claim 1 in which water is combinedwith said azeotrope after said distilling and1-chloro-2,2,2-trifluoroethyl difluoromethyl ether is distilled from themixture.
 6. The method of claim 5 in which the selected member isacetone.
 7. The method of claim 5 in which the selected member is methylethyl ketone.